System and method for determining the data rate capacity of digital subscriber lines

ABSTRACT

A system for determining the data rate capacity of a digital subscriber line includes a communication server coupled to a number of subscribers using twisted pair subscriber lines. A memory coupled to the communication server stores attenuation information and noise information for the twisted pair subscriber lines. A processor coupled to the memory determines the data rate capacity of a selected twisted pair subscriber line using the attenuation information and the noise information.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to and filed concurrently with pending U.S.patent application Ser. No. 09/364,775, entitled “System and Method forDetermining the Transmit Power of a Communication Device Operating onDigital Subscriber Lines” and pending U.S. patent application Ser. No.09/364,332, entitled “System and Method for Determining a CommunicationProtocol of a Communication Device Operating on Digital SubscriberLines.” These applications have been commonly assigned to CiscoTechnology, Inc.

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to data communication, and moreparticularly to determining the data rate capacity of digital subscriberlines.

BACKGROUND OF THE INVENTION

Traditional telephone networks are designed to provide voicetransmissions, and performs this function well. In general, however, theexisting telephone networks are not adept at high speed datatransmission. Digital Subscriber Line technology (DSL) uses existingtwisted pair telephone lines to transport high bandwidth data, such asmultimedia, video on demand, and Internet access, to data servicesubscribers. DSL technology uses a DSL transceiver unit (e.g. modems,splitters, and other communication equipment) at the central office ofthe data services provider and at the subscriber premises to utilize agreater range of frequencies of the telephone line than traditionaltelephone services, resulting in high speed data transmission.

To receive data services, therefore, a subscriber must install theproper communication equipment at the subscriber premises to supporttransmitting and receiving data using DSL technology over the existingtelephone lines. Under certain circumstances, even a subscriber havingthe proper communication equipment may be unable to receive dataservices using particular DSL technologies. Since the communicationequipment required at the subscriber premises may be expensive and thequality of data services received is uncertain, a potential dataservices subscriber may request from the data services provider anestimate of the data rate capacity of the telephone line servicing thepotential subscriber before installing the communication equipment.

The data rate capacity of an existing telephone line generally definesthe maximum throughput of the telephone line and typically depends on anumber of factors. For example, the data rate capacity of a particulartelephone line depends on the length of the telephone line, the gauge ofwiring used in the telephone line, and the number and type of noise orinterference producing elements present near the telephone line. Atypical telephone line may be arranged in one or more binder groupsegments. In general, a binder group segment comprises a collection oftelephone lines that share a common sheath. Each of the factors whichaffects the data rate capacity of a particular telephone line may varyamong the different binder group segments of that telephone line. Inaddition, the provisioning of data services to a subscriber premisesover a telephone line in a particular binder group may contribute to thenoise and distortion upon other telephone lines within the same bindergroup, thereby degrading the services already provided to othersubscriber premises.

Due to the number of factors affecting the data rate capacity of aparticular telephone line, data services providers often cannot providean accurate estimate of the data rate capacity to a potentialsubscriber. In some cases, a data services provider may perform a “truckroll”—the dispatch of a service technician to install communicationequipment or to configure the telephone line at the customer premises—todetermine the-data rate capacity of a particular telephone line. A truckroll, however, is time consuming and cost prohibitive for the dataservices provider and the subscriber.

SUMMARY OF THE INVENTION

In accordance with the present invention, a system for determining thedata rate capacity of digital subscriber lines is provided whichsubstantially eliminates or reduces disadvantages and problemsassociated with previous communication systems.

In accordance with one embodiment of the present invention, a system fordetermining the data rate capacity of a twisted pair subscriber lineincludes a communication server coupled to a number of subscribers usinga number of subscriber lines. The system includes a memory coupled tothe communication server that stores attenuation information and noiseinformation for the subscriber lines. A processor coupled to the memorydetermines the data rate capacity of a selected subscriber line usingthe attenuation information and the noise information.

Another embodiment of the present invention is a method for determiningthe data rate capacity of a twisted pair subscriber line. The methodincludes storing attenuation information and noise information for anumber of twisted pair subscriber lines that couple a number ofsubscribers to a communication server. The method concludes bydetermining the data rate capacity of a selected subscriber line usingthe attenuation information and the noise information.

Technical advantages of the present invention include a system fordetermining the data rate capacity of a twisted pair subscriber linethat includes a communication server, a memory, and a processor. Thememory stores attenuation information, noise information, or any othersubscriber line information for a plurality of subscriber lines. Theprocessor determines the data rate capacity of a selected subscriberline using the attenuation information and the noise information. Inthis respect, a data services provider in the system may pre-provisiondata rates for the subscriber line of a subscriber prior to activatingdata services for the communication equipment at the subscriberpremises.

An important advantage of the system is that the communication serverincludes one or more communication devices that support determiningsubscriber line information while providing data services to subscribersduring operation. The processor collects the subscriber line informationfrom the communication server for storage in the memory. In thisrespect, the processor may collect subscriber line information from anumber of communication servers in the system.

Another advantage of the system is that the memory can store attenuationinformation for a particular subscriber line based upon the constituentbinder group segments of the subscriber line. The processor may thendetermine the attenuation information of a selected subscriber lineaccording to the attenuation characteristics contributed by each of itsconstituent binder group segments. In this respect, the system may moreaccurately determine the data rate capacity of a selected subscriberline.

Another advantage of the present invention is a system for determiningthe transmit power of a communication device operating on a subscriberline of the system. The system includes a communication server having acommunication device that operates on the subscriber line, a memory, anda processor. The memory stores noise information andcross-channel-coupling information for a plurality of subscriber linesin the system. The processor determines the transmit power of thecommunication device based upon the noise information and thecross-channel-coupling information. By determining the optimal transmitpower of a communication device, the system may provide data services toa subscriber that does not degrade the data services provided to othersubscribers.

A further advantage provided by the present invention is that the systemmay select a communication protocol for the communication device that isbest adapted to provided the determined transmit power spectrum. In someinstances when the communication device is inoperable to communicatedata using a first communication protocol, such as an xDSL communicationprotocol, the system may operate the communication device using analternative communication protocol, such as a V-series communicationprotocol. In this respect, a subscriber of the system is less likely tosuffer a loss of data services.

Other technical advantages are readily apparent to one skilled in theart from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumbers indicate like features and wherein:

FIG. 1 illustrates a block diagram of a communication system thatprovides telephone and data service to subscribers in accordance withthe present invention;

FIG. 2 illustrates one arrangement of subscribers in the communicationsystem;

FIG. 3 illustrates one example of subscriber line information stored ina database of the communication system;

FIG. 4 illustrates one example of communication device informationstored in a database of the communication system;

FIG. 5 illustrates a method for managing subscriber line information forthe communication system;

FIG. 6 illustrates a method for determining the transmit power ofcommunication devices operating on a subscriber line of thecommunication system;

FIG. 7 illustrates a method for determining the data rate capacity of asubscriber line of the communication system; and

FIG. 8 illustrates a method for determining a communication protocol ofa communication device operating on a subscriber line of thecommunication system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a communication system 10 that provides bothtelephone and data services to subscribers 12. Each of several centraloffices. 14 is coupled to a number of subscribers 12 using subscriberlines 16. A system management server 18 is coupled to each centraloffice 14 using a data link 20. A system management database 22 iscoupled to each central office 14 using a data link 24 and coupled toserver 18 using a data link 26. In general, database 22 storessubscriber line information 28 and communication device information 29defining the physical and operating characteristics of subscriber lines16 and communication devices 60 of communication system 10,respectively. In one aspect of operation, system management server 18determines the approximate data rate capacity of selected subscriberlines 16 for subscribers 12 using subscriber line information 28 storedin database 22. In another aspect of operation, server 18 determines theoptimal transmit power for a communication device operating on asubscriber line 16. In yet another aspect of operation, server 18determines that a communication device 60 is inoperable to communicatewith a communication device 42 using a first communication protocol and,in response, initiates the operation of communication device 60 using analternative communication protocol.

Subscriber 12 includes a telephone 30 and a computer 32, both coupled toan interface 34. A splitter 36 is coupled to subscriber line 16 andoperates to split subscriber lines 16 into a twisted pair phone line 38and a twisted pair data line 40. In a particular embodiment of system 10employing the “G.lite” standards of the International TelecommunicationsUnion—Telecommunications Standard Section, splitter 36 need not be used.Phone line 38 is coupled to telephone 30 using interface 34. Similarly,data line 40 is coupled to computer 32 using interface 34. Subscriber 12refers to the subscriber premises shown in FIG. 1, one or morecomponents at the subscriber premises, as well as the user of thesecomponents.

Telephone 30 is a traditional telephone transceiver, a cordlesstelephone transceiver, or any other device suitable for allowingcommunication over telephone line 38. Computer 32 comprises a mainframedevice, mini-frame device, server, desktop personal computer, notebookpersonal computer, or other suitable computing device. A computer 32 ofa subscriber 12 already equipped to receive data service fromcommunication system 10 includes an xDSL modem 42 that communicates datausing data line 40. Subscribers 12 seeking to obtain but which do notcurrently receive data service from communication system 10 may or maynot yet be equipped with a modem 42, and are generally referred to asnew subscribers 12. Modem 42 couples to other components of computer 32using a Peripheral Component Interconnect (PCI) bus, an IndustrialStandard Architecture (ISA) bus, a Personal Computer Memory CardInternational Association (PCMCIA) Interface, or any other suitabletechnology that provides input/output capability to computer 32. Theselection and design of modem 42 for computer 32 may depend on the typeor functionality of computer 32, the data rate capacity supported bydata line 40, and the communication protocols supported by centraloffice 14, as described in greater detail below.

Modem 42 comprises any suitable communication device that transmits andreceives data in communication system 10 using any suitable digitalsubscriber line technology (xDSL), referred to generally as an xDSLcommunication protocol. Modem 42 also supports Ethernet; fast Ethernet;V-series data protocols such as V.32bis, V.32terbo, V.34, V.42, V.42bis,and V.90; data frame relay; Asynchronous Transfer Mode (ATM); switchedmulti-mega-bit data service (SMDS); high level data link control (HDLC);serial line Internet protocol (SLIP); point-to-point protocol (PPP);transmission control protocol/Internet protocol (TCP/IP); or any otherappropriate protocol, collectively referred to as digital communicationprotocols. Digital communication protocols and xDSL communicationprotocols may be generically and/or collectively referred to ascommunication protocols. Computer 32 may include a network interface toreceive data from central office 14 or to further communicate data to alocal area network (LAN), wide area network (WAN), or other suitablenetwork coupled to computer 32 using link 44. In general, modem 42translates information between the communication protocol supported bycommunication system 10 and the digital protocol supported by computer32.

Interface 34 couples phone line 38 to telephone 30, and data line 40 tocomputer 32. In one embodiment, interface 34 provides additionalcouplings to additional telephones 30 and computers 32 at subscriber 12.Splitter 36 is a passive or active splitter that divides subscriber line16 into phone line 38 and data line 40 of the same type. Throughout thisdescription, phone line 38 and data line 40 may be referred tospecifically, or collectively as part of subscriber line 16.

Communication system 10 includes a plurality of central offices 14coupled to system management server 18 and system management database22. Each central office 14 is coupled to subscribers 12 using twistedpair subscriber lines 16. In an exemplary embodiment, each centraloffice 14 provides phone and data service to many subscribers, with eachsubscriber 12 including one or more components described above at itspremises. The subscribers and subscriber lines in communication system10 are referred to collectively in the plural as subscribers 12 andsubscriber lines 16.

Subscriber line 16 couples subscriber 12 to central office 14.Subscriber line 16 comprises twisted pair wiring that is commonlyinstalled at subscriber premises and as the local loop in many publicswitched telephone networks (PSTNs). Subscriber line 16 may beunshielded twisted pair (UTP), shielded twisted pair (STP), or any othersuitable type or category of twisted pair wiring made of copper or othersuitable material. Phone line 38 and data line 40 associated withsubscriber line 16 may be the same or different type or category oftwisted pair wiring. A subscriber line 16 between central office 14 anda particular subscriber 12 may be arranged in a binder group 45comprising one or more binder group segments 46. In general, a bindergroup segment 46 comprises a collection of subscriber lines 16 thatshare a common “sheath.” Interference between subscriber lines 16 in abinder group 45 presents a level of complexity in xDSL deployment, asdescribed in greater detail below with regard to FIG. 2.

In general, communication system 10 employs xDSL technology to providehigh-bandwidth downlink data rates 80 and uplink data rates 82 forsubscriber lines 16. Data rates 80 and 82 comprise a measure of thenumber of data bits that may be transmitted by subscriber line 16 fromcentral office 14 to subscriber 12 and from subscriber 12 to centraloffice 14, respectively, as a function of time. Typically, data rates 80and 82 of a subscriber line 16 depend on a number of physical andoperational characteristics of the subscriber line 16, including thelength of subscriber line 16; its wire gauge; and the presence ofbridged taps, cross-coupled interference, or any other noise orinterference producing elements, generally referred to as disturbers, insystem 10. Information defining the physical and operationalcharacteristics of a subscriber line 16 is generally referred to assubscriber line information 28.

Downlink data rate 80 and uplink data rate 82 depend on the specificcommunication protocol employed, the quality and length of subscriberline 16, the contribution of noise and distortion from other componentsin communication system 10, and any other physical or operationalcharacteristics of a subscriber line 16. A particular advantage providedby communication system 10 is that system management server 18 mayapproximate downlink data rate 80 and uplink data rate 82 for aparticular subscriber line 16 using the physical and operationalcharacteristics of the particular subscriber line 16 and othersubscriber lines 16 as indicated by subscriber line information 28stored in database 22. In this regard, a central office 14 maypre-provision data rates 80 and 82 for a subscriber line 16 of a newsubscriber 12 prior to activating data services for modem 42 or for anyother communication equipment at subscriber premises 12.

Central office 14 includes a splitter 50 coupled to subscriber lines 16.Like splitter 36 at subscriber 12, splitter 50 at central office 14 is apassive or active splitter that divides subscriber line 16 into atwisted pair phone line 52 and a twisted pair data line 54. Phone line52 and data line 54 associated with subscriber line 16 may be the sameor different type or category of twisted pair wiring. A telephone switch56 at central office 14 is coupled to phone line 52 to provide plain oldtelephone system (POTS) service to subscriber 12. Telephone switch 56also represents other components in the PSTN or other suitable voicecommunication network, such as switches, wireline or wireless links,satellites, microwave links, and other communication facilities todeliver telephone service to subscriber 12.

A communication server 58 comprises any suitable combination of hardwareand software that resides at central office 14, at a remote terminal, orany other suitable access point in system 10 that allows coupling tolocal loops formed by subscriber lines 16. In one embodiment, acommunication server 58 couples to splitter 50 of central office 14using data line 54. Generally, communication server 58 manages theprovisioning of data service to subscriber 12, and includes modems 60coupled to a controller 62 using a link 64.

A modem 60 comprises any suitable communication device that transmitsand receives data in communication system 10 using any suitablecommunication protocol supported by subscriber lines 16. Modems 60 maybe integrated into any suitable chipset that includes the appropriatehardware and memory to support the data scrambling and descrambling,encoding and decoding, interleaving and deinterleaving, data insertionand extraction, filtering, amplifying, and other signal processingtechniques employed by the appropriate communication protocols. Modem 60refers to one or more modems at central office 14, as well as any of thecomponents of the modem chipset.

Controller 62 comprises any suitable combination of hardware andsoftware that performs off-hook detection to determine if subscriber 12desires data service and couples a modem 60 to subscriber line 16 upondetecting a need for data service from a computer 32 of subscriber 12.Controller 62 also tracks subscriber usage, monitors subscriberinformation and generates billing and demographic information.

An important advantage of communication server 58 is that modems 60support determining subscriber line information 28 of subscriber lines16 while providing data service to subscribers 12, as described indetail below. System interface controller 74 polls modems 60periodically, in response to an external stimulus, or upon an eventtime-out to collect the subscriber line information 28 for subscriberlines 16 and to communicate it to system management server 18 usinglinks 76 and 20.

Communication server 58 multiplexes modem digital outputs into amultiplexed digital line 66 for delivery to a router or other networkdevice 68. In one embodiment, multiplex digital line 66 carries asingle, bidirectional and multiplexed signal for all subscribers 12 of aparticular central office 14. Signals on multiplexed digital line 66 maysupport any appropriate digital protocol used by network device 68. Inthis regard, communication server 58 and network device 68 may form aportion of a Digital Subscriber Link Access Multiplexer (DSLAM) 69 atcentral office 14. A communication network 70, such as a globalcommunication network like the Internet, is coupled to network device68. Communication network 70 may also include a synchronous opticalnetwork (SONET), a frame relay network, an Asynchronous Transfer Mode(ATM) network, a T1, T3, E1, or E3 network, or any other suitablecommunication network.

System interface controller 74 comprises any suitable system controllercard at DSLAM 69 that supports simple network management protocol(SNMP), or any other suitable protocol that communicates data to systemmanagement server 18 using link 20 and any suitable in-band orout-of-band signaling techniques. In particular, system interfacecontroller 74 communicates to server 18 as SNMP variables the subscriberline information 28 extracted from various components of system 10, suchas from modem 60. Line 20 comprises any suitable switched or dedicatedcommunication path that supports communication between controller 74 andserver 18 using SNMP, or any other suitable protocol. Althoughcontroller 74 is illustrated in FIG. 1 integrated into DSLAM 69 atcentral office 14, it should be understood that one or more controllers74 may alternatively be integrated into and managed by server 18 onbehalf of one or more central offices 14. In this regard, server 18 maycollect subscriber line information 28 from a number of central offices14 in communication system 10.

Database management server 72 may comprise any suitable computingplatform operating database management software that generally stores,updates, and retrieves information. The database management software maybe used to access several different databases stored locally or remotelyfor different purposes within central office 14. In one embodiment, thedatabase management server 72 of a particular central office 14maintains in system management database 22 a portion of subscriber lineinformation 28. Typically, this information includes a subscriber lineidentifier, the length of the subscriber line, the gauge of twisted pairwiring used for the subscriber line, and the number and type ofdisturbers associated with the subscriber line 16. In one embodiment,this information may be stored arranged according to the differentbinder group segments 46 of each subscriber line 16. The databasemanagement software operating on server 72 manages the security and useraccess of the stored information on behalf of central office 14. A userwith proper security clearance may access server 72 and database 22 tostore, update, or retrieve the above-identified subscriber lineinformation 28.

System management server 18 comprises any suitable computing platform100 operating a system management application 102. Computing platform100 includes a processor 104 coupled to one or more output devices 106,such as a display or speaker, and one or more input devices 108, such asa keyboard or mouse. Platform 100 also includes a communicationinterface 110, such as the appropriate hardware (e.g., one or moremodems, terminal adapters, or network interface cards) and software(e.g., protocol conversion and data processing software) to communicatewith modems 60 using interface controller 74. Platform 100 also includesmemory 112 that stores application 102 and any associated files, tables,or buffers, in RAM, ROM, CD-ROM, or any other form of magnetic oroptical storage.

Application 102 comprises a set or collection of instructions,procedures, and/or related data adapted for implementation in a suitablecomputer language such as, for example, C, C++, or any other suitabledevelopment language. Application 102 may be a stand-alone applicationor delivered integral to or with other system management software. Ingeneral, application 102 determines the optimal transmit power spectrumdensity of modems 60 and 42. Application 102 also determines theappropriate communication protocol to use for a modem 60 or 42 providingdata services to a subscriber 12. Application 102 further determines theapproximate data rate capacity 80 and 82 of subscriber lines 16.

System management database 22 comprises any suitable form of memoryarranged, for example, as a data storage facility or a data warehousethat provides a consistent, updated, and integrated view of subscriberline information 28 and communication device information 29 gathered bycentral offices 14 and system management server 18 of system 10.Information 28 and 29 may be stored in files, tables, charts, matrices,or in any other suitable organization of data that is readily accessibleby server 18 and central offices 14. Server 18 and database 22 may bereferred to collectively as a communication facility.

Subscriber line information 28 comprises information defining thephysical and operational characteristics of subscriber lines 16 insystem 10. Information defining the physical characteristics ofsubscriber lines 16 includes a subscriber line identifier, the length ofeach subscriber line 16, the number and arrangement of binder groupsegments 46 for each subscriber line 16, the gauge of twisted pairwiring used in each binder group segment 46 of subscriber line 16, thenumber and type of disturbers for each binder group segment 46 ofsubscriber line 16, cross-channel coupling information for subscriberlines 16, or any other information defining the physical characteristicsof subscriber lines 16. The information defining the physicalcharacteristics of subscriber line 16 may be maintained by either systemmanagement server 18 or by the database management server 72 of eachcentral office 14 in system 10.

The information defining the operational characteristics of subscriberlines 16 includes attenuation information and noise information forsubscriber lines 16 of system 10. The attenuation information and noiseinformation may be determined as a function of the information definingthe physical characteristics of subscriber lines 16 by performingattenuation estimation and noise estimation algorithms. Alternatively,the attenuation information and the noise information of a particularsubscriber line 16 may be determined based upon information acquired bythe appropriate modem pairs (e.g., a modem 60 at central office 14 and amodem 42 at subscriber 12) over a statistically significant period oftime, as described in greater detail below.

Communication device information 29 comprises information defining thephysical characteristics of communication devices in system 10 such asthe number and type of modems 60 available for use, and the type ofcommunication protocols supported by modems 60. Information 29 furthercomprises information defining the operational characteristics ofcommunication devices in system 10, such as the number of times aparticular modem 60 fails to communicate with a particular modem 42using a particular subscriber line 16 and a particular communicationprotocol. Communication device information 29 is described in greaterdetail with reference to FIG. 4.

Communication system 10 supports data service over subscriber lines 16using asymmetric digital subscriber line (ADSL), symmetric digitalsubscriber line (SDSL), high speed digital subscriber line (HDSL), veryhigh speed digital subscriber line (VDSL), or any other suitable xDSLcommunication protocols that allows high rate data service over twistedpair wiring. Each of these xDSL communication protocols provides dataservice using existing subscriber lines 16 without interrupting normaltelephone service. This is accomplished, for example, by a separationtechnique, such as frequency division multiplexing (FDM) or echocancellation, to separate frequencies that provide telephone servicefrom those frequencies that provide data service. Dynamic noisecancellation techniques and a guard band between the data and phoneservice frequencies ensure reliable and simultaneous access to data andphone service over subscriber line 16. For example, subscriber 12 maysimultaneously engage in both a data communication session usingcomputer 32 and a voice conversation using telephone 30.

In one embodiment, subscriber line 16 and components of subscriber 12and central office 14 support communication using ADSL techniques thatcomply with ANSI Standard T1.413, such as discrete multi tone (DMT)modulation. In another embodiment, ADSL communication may be performedusing carrier-less amplitude modulation (CAP). In an ADSL communicationsystem, the downlink data rate 80 from central office 14 to subscriber12 is greater than the uplink data rate 82 from subscriber 12 to centraloffice 14. This allows high bandwidth communication to subscriber 12,while still providing lower bandwidth communication to central office14. ADSL communication is well adapted for applications, such asvideo-on-demand, multi-media, and Internet access, that transfers largevolumes of information to subscriber 12 in response to shorter requestsfor information. Although portions of the following description of theoperation of system 10 are detailed in terms of communication using ADSLtechniques, it should be understood that the features and functions ofsystem 10 also apply to the other xDSL communication protocols discussedabove.

In operation, communication system 10 generally provides phone and dataservices to those subscribers 12 having the proper communicationequipment at the subscriber premises. To access data services, inparticular, a subscriber 12 operates a modem 42 that exchanges data witha modem 60 of a central office 14 using any suitable communicationprotocol.

The provisioning of data services to a new subscriber 12 over asubscriber line 16 in a particular binder group 45 may contribute to thenoise and distortion upon other subscriber lines 16 within the samebinder group 45, thereby degrading the services already provided toother subscribers 12. Therefore, a central office 14 may endeavor toprovide data services to a new subscriber 12 that does not degrade theservices provided to other subscribers 12 by determining an optimaltransmit power spectrum density of modems 60 and 42 operating onsubscriber lines 16 for new subscribers 12 and by selecting thecommunication protocol that is best adapted to provide the determinedpower spectrum density.

Because the downlink data rate 80 and uplink data rate 82 of aparticular subscriber line 16 varies depending on the specificcommunication protocol employed, the quality and length of thesubscriber line 16, and the contribution of noise and distortion fromdisturbers within system 10, a new subscriber 12 may request from acentral office 14 approximations for data rates 80 and 82 supported bythe subscriber line 16 before activating modem 42. In some cases,central offices 14 provide inaccurate estimations of data rates 80 and82. In other cases central offices 14 must perform a “truck roll”—thedispatch of a service technician to activate a modem 42 or to configurea subscriber line 16—prior to determining data rates 80 and 82. This maybe time consuming and cost prohibitive for central offices 14 andsubscribers 12.

The system management server 18 of system 10 supports determining andcontrolling the power spectrum density of modems 60 and 42, anddetermining data rate capacity 80 and 82 for a particular subscriberline 16 using subscriber line information 28 stored in system managementdatabase 22. In particular, system management server 18 extractssubscriber line information 28 from various components of system 10,such as modems 60 of central offices 14; processes information 28 forstorage in system database 22; and accesses selected subscriber lineinformation 28 stored in database 22 to determine the appropriate powerspectrum density of modems 60 and 42 and the approximate data ratecapacity 80 and 82 of subscriber lines 16. In this regard, server 18manages the various components of system 10.

In addition to storing subscriber line information 28 collected bydatabase management servers 72 of central offices 14, system managementdatabase 22 stores information 28 processed by system management server18, such as attenuation information and noise information. Server 18extracts subscriber line information 28 from various components ofsystem 10, such as modems 60 of communication server 58, using systeminterface controller 74.

Modems 60 may collect information defining the operationalcharacteristics of subscriber lines 16 while providing data services tosubscribers 12. This process of gathering subscriber line information 28is referred to as “modem training,” and generally occurs during thenormal course of operation of system 10. Although the followingdescription of modem training is detailed with reference to ADSL modemsthat employ discrete multi-tone (DMT) modulation technology, it shouldbe understood that other types of modems employing other modulationtechnology may gather information defining the operationalcharacteristics of a subscriber line 16 using suitable techniques.Therefore, one of skill in the art can appreciate that the transmitpower spectrum density and data rate determination features andfunctions performed by server 18 are not limited to any particular typeof communication protocol or modulation technology.

ADSL modems 60 increase the amount of data that the conventionaltwisted-pair subscriber lines 16 can carry by using DMT technology todivide the bandwidth of a subscriber line 16, generally referred to asthe frequency spectrum supported by a subscriber line 16, into manyindividual sub-bands or channels. Each channel of a subscriber line 16uses a form of quadrature amplitude modulation (QAM) to transmit data ineach channel simultaneously. For example, the 1.1 MHz frequency spectrumof a conventional twisted pair subscriber line 16 may be divided suchthat the lower 4 kHz is reserved for use by POTS and is generallyreferred to as the voice frequency spectrum. The frequency range from 25kHz to 1.1 MHz, generally referred to as the data frequency spectrum, isdivided into sub-frequencies. Each sub-frequency is an independentchannel and supports transmission of its own stream of data signals. DMTtechnology is very useful for ADSL technology where the sub-channels aredivided into groups and one group of channels is allocated for theuplink transmission of data and the other for the downlink transmissionof data.

During modem training, an ADSL modem 60 employing DMT modulationtechnology may collect subscriber line information 28 used to determineattenuation information and noise information for each channel of thedata frequency spectrum for a particular subscriber line 16. To collectsubscriber line information 28 for subscriber line 16 during thedownlink transmission of data, for example, modem 60 transmits a datasignal at a known transmit power spectrum density, Q_(f), for eachchannel of the data frequency spectrum allocated for downlinktransmission. Modem 42 measures the received signal power spectrumdensity, S_(f), of the received data signal for each downlink channeland communicates this and other subscriber line information 28 to modem60.

In some situations, modems 60 and 42 may not establish a connection overthe entire frequency spectrum of a subscriber line 16. Rather, themodems 60 and 42 may only connect over a subrange of frequencies. Inthese instances where a modem 60 fails to operate over the entirefrequency spectrum supported by a subscriber line 16, central office 14may enter a modem 60 into a diagnostic mode. In the diagnostic mode, amodem 60 communicates to modem 42 a signal pulse at a known transmitpower spectrum density, Q_(f), for one or more sub-frequencies withinthe frequency spectrum over which the modems 60 and 42 may stillconnect, such as over a sub-frequency in the voice frequency spectrum.

Modem 42 at subscriber premises 12 receives the data signal that iscommunicated by modem 60 and determines subscriber line information 28,such as attenuation information, noise information, received signalpower spectrum density, S_(f), or any other information describing thephysical or operating characteristics of subscriber line 16 at the oneor more sub-frequencies over which the connection between modem 60 and42 is established. Modem 42 then extrapolates subscriber lineinformation 28 for all frequencies in the frequency spectrum supportedby subscriber line 16 and communicates the determined subscriber lineinformation 28 to central office 14 over any achievable range ofsub-frequencies using any suitable communication protocols, such as, forexample, over a sub-frequency in the voice frequency spectrum using theV.90 communication protocol.

In those instances where modems 60 and 42 fail to establish a connectionusing a particular communication protocol, such as an xDSL communicationprotocol, server 18 may initiate the operation of modem 60 using analternative communication protocol. For example, if the number of timesa modem 60 fails an attempt to communicate with a modem 42 using a firstcommunication protocol exceeds a predetermined threshold, then server 18initiates the operation of the particular modem 60 using an alternativecommunication protocol supported by the particular subscriber line 16.This aspect of operation of system 10 is described in further detailwith respect to FIGS. 4 and 8.

Upon an event time-out, after a suitable period of time, in response toinstructions from system management server 18, or before modem 60operates on another subscriber line 16, system interface controller 74extracts from modem 60 subscriber line information 28, such as thetransmit power spectrum density, Q_(f), and the received signal powerspectrum density, S_(f), measurements for each channel of eachsubscriber line 16 upon which the modem 60 operated, and communicatesthis information 28 to server 18 for further processing.

Server 18 then determines the attenuation information and noiseinformation for subscriber lines 16. In particular, the transferfunction of a subscriber line 16 at any particular sub-frequency ofcommunication, such as frequencies supported by subscriber line 16 fordownlink or uplink transmission of data, is generally referred to asattenuation information and may be modeled by the following equation:${H_{f}} = \sqrt{\frac{S_{f}}{Q_{f}}}$

where: H_(f)=attenuation information for subscriber line 16 atsub-frequency (f);

Q_(f)=power spectrum density of a signal transmitted at sub-frequency(f); and

S_(f)=power spectrum density of the signal received at sub-frequency(f).

The loop insertion loss for any particular sub-frequency may then bemodeled by the following equation:

Insertion loss_(dB)=−201og₁₀(|H_(f)|)

where: |H_(f)|=attenuation information for subscriber line 16 atsub-frequency (f).

Therefore, the attenuation information of subscriber line 16 atsub-frequencies supporting the downlink transmission of data may beobtained by measuring the power spectrum density, Q_(f), of a signaltransmitted by modem 60, and the power spectrum density, S_(f), of thesignal received by modem 42, and performing the appropriate attenuationinformation modeling techniques as described above. Similarly, theattenuation information of subscriber line 16 at sub-frequenciessupporting the uplink transmission of data may be obtained by measuringthe power spectrum density, Q_(f), of a signal transmitted by modem 42,and the power spectrum density, S_(f), of the signal received by modem60, and performing the appropriate attenuation information modelingtechniques as described above.

The noise information for a particular subscriber line 16 may bedetermined by measuring noise characteristics of a subscriber line 16during operation or by calculating the noise information usingsubscriber line information 28 for subscriber line 16. For example, amodem 42 of a subscriber 12 may operate as a spectrum analyzer duringoperation to sample a time domain signal communicated by central office14 using subscriber line 16. Modem 42, operating as a spectrum analyzer,measures the noise variance of the time domain signal over astatistically significant period of time and converts the measured noisevariance from the time domain to the frequency domain by performing, forexample, a Fast Fourier Transform.

If modem 42 is not subscribed to receive data services from centraloffice 14, then modem 42 may communicate the measured noise information,such as the noise variance for the signal determined for the frequencydomain, to central office 14 over any suitable range of sub-frequenciesusing any suitable communication protocol, such as, for example, over asub-frequency in the voice frequency spectrum using the V.90communication protocol. If modem 42 is subscribed to receive dataservices from central office 14, then modem 42 may communicate themeasured noise information to modems 60 of central office 14 using anysuitable communication protocol and frequencies supported by subscriberlines 16.

The noise information for any particular subscriber line 16 mayalternatively be calculated using subscriber line information 28. Theelectrical energy transmitted across a subscriber line 16 as a modulatedsignal also radiates energy onto adjacent subscriber lines 16 located inthe same binder group 45. This cross-coupling of electromagnetic energyis called cross-talk. In communication system 10, adjacent subscriberlines 16 within a binder group 45 that transmit or receive informationin the same range of frequencies can create significant cross-talkinterference. This is because cross-talk-induced signals combine withthe signals which were originally intended for transmission oversubscriber line 16 and results in a slightly different shaped waveformthan was originally transmitted. Cross-talk can be categorized in one oftwo forms. Near End cross-talk, commonly referred to as NEXT, is themost significant form of cross-talk because the high energy signal froman adjacent system can induce relatively significant cross-talk into theprimary signal. The other form of cross-talk is Far End cross-talk, orFEXT. FEXT is typically less of an issue because the far end interferingsignal is attenuated as it traverses subscriber line 16.

Using subscriber line information 28 regarding the number and types ofcross-talk creating components, generally referred to as disturbers, inthe binder group 45 to which the particular subscriber line 16 belongsand their transmit power spectrum density, the noise caused by Near Endcross-talk upon subscriber line 16 may be modeled by the followingequation:${n_{f}({NEXT})} = {\left( \frac{N}{49} \right)^{.6}\quad \frac{\left( Q_{f} \right)\left( f^{3/2} \right)}{1.134 \times 10^{13}}}$

where: n_(f)(NEXT)=noise caused by NEXT upon subscriber line 16 atsub-frequency (f);

N=number of disturbers of a particular type;

Q_(f)=transmit power spectrum density of disturbers at sub-frequency(f); and

f=sub-frequency of communication.

If multiple types of disturbers (e.g., HDSL, ADSL, SDSL, ISDN, T1, E1,etc.) exist within binder group 45 of subscriber line 16, then the noisecreated upon subscriber line 16 by the total number of disturbers may bedetermined as the summation of the noise contributions upon subscriberline 16 by each type of disturber, as modeled by the following equation:n_(f)(NEXT) = n_(f)(NEXT_(HDSL)) + n_(f)(NEXT_(SDSL)) + n_(f)(NEXT_(ADSL)) + n_(f)(NEXT_(ISDN)) + … + n_(f)(NEXT_(T1)).

The noise caused by Far End cross-talk upon subscriber line 16 may bemodeled by the following equation:${n_{f}({FEXT})} = {\left( \frac{N}{49} \right)^{.6}\quad {{kdf}^{2}\left( {H_{f}}^{2} \right)}Q_{f}}$

where:

n_(f)(FEXT)=noise caused by FEXT upon subscriber line 16 atsub-frequency (f);

N=number of disturbers of a particular type;

k=8×10⁻²⁹;

d=length of subscriber line 16 measured in feet;

|H_(f)|32 attenuation information for subscriber line 16 atsub-frequency (f);

Q_(f)=transmit power spectrum density of disturbers at sub-frequency(f); and

f=sub-frequency of communication.

Again, if multiple types of disturbers exist within the relevant bindergroup of subscriber line 16, then the noise created by Far Endcross-talk upon subscriber line 16 by the total number of disturbers maybe determined as the summation of the noise contributions uponsubscriber line 16 by each type of disturber, as modeled by thefollowing equation:n_(f)(NEXT) = n_(f)(FEXT_(HDSL)) + n_(f)(FEXT_(SDSL)) + n_(f)(FEXT_(ADSL)) + n_(f)(FEXT_(ISDN)) + … + n_(f)(FEXT_(T1)).

Therefore, the total noise created by Near End cross-talk and Far Endcross-talk upon subscriber line 16 may be modeled by the followingequation:

n _(f) =n _(f)(NEXT)+n _(f)(FEXT)

However, because the far end interfering signal is attenuated as ittraverses subscriber line 16, the contributions to noise upon subscriberline 16 by FEXT are negligible as compared to those of NEXT.

System management server 18 updates subscriber line information 28stored in database 22 with the determined attenuation information andnoise information for subscriber lines 16. By determining attenuationinformation and noise information for subscriber lines 16 over astatistically significant period of time, server 18 maintains theintegrity of subscriber line information 28 stored in database 22.System management server 18 may determine and database 22 may storesubscriber line information 28 according to a particular subscriber line16 or the different binder group segments 46 of the particularsubscriber line 16.

System management server 18 determines the transmit power spectrumdensity, Q_(f), of a modem 60 or 42 operating on a particular subscriberline 16 using subscriber line information 28 stored in database 22.Server 18 then determines the communication protocol that is bestadapted to provide the determined transmit power spectrum density ofmodem 60 or 42. The transmit power spectrum density for a modem 60 or 42operating on a particular subscriber line 16 may be modeled by thefollowing equation to minimize the effect of the interference caused bythe subscriber line 16 upon other subscriber lines 16 within the samebinder group 45: $Q_{f} = \frac{n_{f}}{{\hat{x}}_{f}}$

where: Q_(f)=transmit power spectrum density;

n_(f)=noise caused by disturbers of system 10 upon the particularsubscriber line 16; and${\hat{x}}_{f} = {\left( \frac{1}{49} \right)^{.6}\quad \frac{f^{3/2}}{1.134 \times 10^{13}}}$

Server 18 determines the communication protocol that is best adapted toprovide the determined transmit power spectrum density of modem 60 or 42for the frequency spectrum supported by subscriber line 16. For example,server 18 may determine that ADSL technology is appropriate to provide atransmit power spectrum density that is substantially low from 0 kHz to128 kHz and that is substantially high from 129 kHz to 1.1 MHz. Server18 may determine that VDSL technology is appropriate to provide atransmit power spectrum density that is substantially high from 0 kHz to128 kHz and that is substantially low from 129 kHz to 1.1 MHz. Server 18may determine that SDSL technology is appropriate to provide a transmitpower spectrum density that is substantially high throughout thefrequency spectrum from 0 kHz to 1.1 MHz. Server 18 may determine thatany type of xDSL technology is appropriate to provide a transmit powerspectrum density that is substantially low throughout the frequencyspectrum from 0 kHz to 1.1 MHz.

System management server 18 determines the approximate uplink anddownlink data rate capacity 80 or 82 of a selected subscriber line 16using subscriber line information 28 stored in database 22. In oneembodiment, server 18 determines data rate capacity 80 or 82 of aselected subscriber line 16 using the determined transmit power spectrumdensity of a modem 42 or 60 operating on the subscriber line 16. Server18 retrieves subscriber line information 28 from database 22, such asthe appropriate attenuation information and noise information, accordingto the selected subscriber line 16, a representative subscriber line 16,or the constituent binder group segments 46 of the selected subscriberline 16.

Server 18 retrieves attenuation information for the selected subscriberline 16 using one of two methods. According to a first method, server 18searches subscriber line information 28 to locate another subscriberline 16 having each of the same binder group segments 46 as the selectedsubscriber line 16. Such a subscriber line 16 is generally referred toas a representative subscriber line 16. If server 18 locates arepresentative subscriber line 16, then it retrieves the attenuationinformation for the representative subscriber line 16 for determinationof the data rate capacity 80 or 82 of the selected subscriber line 16,as described in detail below.

According to a second method to retrieve attenuation information, server18 searches subscriber line information 28 to locate each individualbinder group segment 46 of the selected subscriber line 16. Each of theindividual binder group segments 46 of the selected subscriber line 16is generally referred to as a representative binder group segment 46 andmay be located in database 22 associated with one or more subscriberlines 16. Server 18 identifies the attenuation information for eachrepresentative binder group segment 46 and associates each of theirindividual attenuation contributions for each downlink and uplinkchannel of transmission to determine the approximate total attenuationinformation for each channel of the selected subscriber line 16.

Server 18 also retrieves noise information for the selected subscriberline 16 using one of two methods. According to a first method, server 18retrieves the noise information stored in database 22 for the selectedsubscriber line 16 itself. According to a second method, server 18searches subscriber line information 28 to locate another subscriberline 16 having each of the same binder group segments 46 as the selectedsubscriber line 16. If server 18 locates such a representativesubscriber line 16, then it retrieves the noise information for therepresentative subscriber line 16 for determination of the data ratecapacity 80 or 82 of the selected subscriber line 16 as described indetail below. The noise information for the selected subscriber line 16or for the representative subscriber line 16 may have been collected bya modem 42 operating as a spectrum analyzer and communicated to centraloffice 14, as described above. Alternatively, the noise information forthe selected subscriber line 16 or for the representative subscriberline 16 may have been calculated according to the equations for Near Endcross-talk and Far End cross-talk modeled above.

Using the determined attenuation information and noise information,server 18 determines the signal-to-noise ratio of a signal communicatedby modem 60 or 42 over subscriber line 16 at a particular sub-frequency,according to the following equation:${SNR}_{f} = \frac{\left( Q_{f} \right)\left( {H_{f}}^{2} \right)}{n_{f}}$

where: SNR_(f)=signal to noise ratio of signal;

Q_(f)=transmit power spectrum density at sub-frequency (f);

|H_(f)|=attenuation information for subscriber line 16 at sub-frequency(f); and

n_(f)=noise information for subscriber line 16 at sub-frequency (f).

Therefore, server 18 may determine the signal-to-noise ratio of a datasignal communicated by modem 42 over subscriber line 16 by using thetransmit power spectrum density, Q_(f), of modem 42, the attenuationinformation for subscriber line 16, |H_(f)|, and the noise informationfor subscriber line 16, n_(f), at sub-frequencies supporting the unlinktransmission of data. Similarly, server 18 may determine thesignal-to-noise ratio of a data signal communicated by modem 60 oversubscriber line 16 by using the transmit power spectrum density, Q_(f),of modem 60, the attenuation information for subscriber line 16,|H_(f)|, and the noise information for subscriber line 16, n_(f), atsub-frequencies supporting the downlink transmission of data.

The uplink data rate capacity 82 is a measure of the amount of data bitsthat may be transmitted by subscriber line 16 from subscriber 12 tocentral office 14 as a function of time, and may be modeled by thefollowing equation:$R = {\frac{1}{T}{\underset{f = f_{1}}{\sum\limits^{f_{2}}}{\log_{2}\left\lbrack {1 + \frac{{SNR}_{f}}{9.55}} \right\rbrack}}}$

where: R=uplink data rate capacity 82;

1/T=baud rate of modem 42;

SNR_(f)=signal-to-noise ratio of subscriber line 16 at sub-frequenciessupporting the uplink transmission of data;

f₁=low frequency boundary for uplink data frequency spectrum; and

f₂=high frequency boundary for uplink data frequency spectrum.

The downlink data rate capacity 80 is a measure of the amount of databits that may be transmitted by subscriber line 16 from central office14 to subscriber 12 as a function of time, and may be modeled by thefollowing equation:$R = {\frac{1}{T}{\underset{f = f_{3}}{\sum\limits^{f_{4}}}{\log_{2}\left\lbrack {1 + \frac{{SNR}_{f}}{9.55}} \right\rbrack}}}$

where: R=downlink data rate capacity 80;

1/T=baud rate of modem 60;

SNR_(f)=signal-to-noise ratio of subscriber line 16 at sub-frequenciessupporting the downlink transmission of data;

f₃=low frequency boundary for downlink data frequency spectrum; and

f₄=high frequency boundary for downlink data frequency spectrum.

FIG. 2 illustrates an exemplary arrangement of subscriber lines 16comprising different binder group segments 46 in system 10. Generally, abinder group segment 46 is a collection of subscriber lines 16 thatshare a common “sheath”. A particular subscriber line 16 may extend fromcentral office 14 to a subscriber 12 through a number of differentbinder group segments 46. The provisioning of data services to a newsubscriber 12 over a subscriber line 16 in a particular binder groupsegment 46 may contribute to the noise and distortion upon othersubscriber lines 16 within the same binder group segment 46, therebydegrading the services already provided to other subscribers 12.Therefore, a central office 14 may endeavor to provide data services toa new subscriber 12 that does not degrade the services provided to othersubscribers 12 by determining an optimal transmit power spectrum densityof modems 60 and 42 operating on subscriber lines 16 for new subscribers12 and by selecting the communication protocol that is best adapted toprovide the determined power spectrum density.

Although the following description of FIG. 2 details the determinationof a power spectrum density for a modem 60 operating on a subscriberline 16 d for a new subscriber 12 d, it should be understood that thefollowing determination of a transmit power spectrum density may applyfor either modem 60 or 42 and for any subscriber 12. The cross-talkcaused by subscriber line 16 d upon subscriber lines 16 sharing a commonbinder group segment 46, such as subscriber lines 16 c and 16 e ofbinder group segments 46 cde and 46 bde, will degrade the data servicesoffered to subscribers 12 c and 12 e unless the noise contributed bysubscriber line 16 of subscriber 12 is maintained below a determined“noise floor.”

The signal-to-noise-interference ratio for subscriber lines 16 c and 16e may be modeled by the following equations:${SNIR}_{c} = \frac{Q_{c}\left( H_{c}^{2} \right)}{n_{c} + X_{e,c} + X_{d,c}}$

where: X_(e,c)=Q_(c){circumflex over (X)}_(e,c);

X_(d,c)=Q_(c){circumflex over (X)}_(d,c); and

n_(c)=noise information for subscriber line 16 c.${SNIR}_{e} = \frac{Q_{e}\left( H_{e}^{2} \right)}{n_{e} + X_{c,e} + X_{d,e}}$

where: X_(c,e)=Q_(e){circumflex over (X)}_(c,e);

X_(d,e)=Q_(e){circumflex over (X)}_(d,e); and

n_(e)=noise information for subscriber line 16 e.

Because the contribution of noise to subscriber line 16 c by subscriberline 16 d for new subscriber 12 dcomprises X_(d,c), the transmit powerspectrum density, Q, of a modem 60 or 42 operating on subscriber line 16d is controlled such that Q_(c){circumflex over (X)}_(d,e)≦n_(c) so thatX_(d,c) does not substantially affect SNIR_(c). Similarly, because thecontribution of noise to subscriber line 16 e by subscriber line 16 dcomprises X_(d,e), the transmit power spectrum density, Q, of a modem 60or 42 operating on subscriber line 16 d is controlled such thatQ_(e){circumflex over (X)}_(d,e)≦n_(e) so that X_(d,e), does notsubstantially affect SNIR_(e). In this respect, the optimal transmitpower spectrum density of a modem 60 or 42 operating on subscriber line16 d may be determined using the noise information of subscriber lines16 c and 16 e as a “noise floor.” For example, the lowest noiseinformation of subscriber lines 16 c and 16 e may be used as the “noisefloor” in the transmit power spectrum density determination.

Alternatively, the optimal transmit power spectrum, density of a modem60 or 42 operating on subscriber line 16 d may be determined using thenoise information of the subscriber line 16 for the new subscriber 12,such as subscriber line 16 d of new subscriber 12 d, as a “noise floor.”In particular, because the cross-channel coupling, {circumflex over(x)}, caused by subscriber line 16 d upon either subscriber line 16 c or16 e is substantially similar to the cross-channel coupling, {circumflexover (x)}, caused by subscriber lines 16 c and 16 e upon subscriber line16 d, respectively, the contribution of noise by subscriber line 16 dupon subscriber lines 16 c and 16 e may be minimized by controlling thetransmit power spectrum density of a modem 60 or 42 operating onsubscriber line 16 d such that Q_(d)x̂ ≤ n_(d)${\text{where:}\quad \hat{x}} = {\left( \frac{1}{49} \right)^{.6} \cdot {\frac{f^{3/2}}{1.134 \times 10^{13}}.}}$

Alternatively, {circumflex over (x)} may be measured for subscriberlines 16.

Therefore, the optimal transmit power spectrum density for a modem 60operating on subscriber line 16 d may be modeled by the followingequation:$Q_{f} = \frac{n_{f}}{\left( \frac{1}{49} \right)^{.6}\frac{f^{3/2}}{1.134 \times 10^{13}}}$

where: Q_(f)=determined transmit power spectrum density of modem 60 or42 operating on subscriber line 16 for subscriber 12 at sub-frequency(f);

n_(f)=noise information for subscriber line 16 at sub-frequency (f); and

f=sub-frequency of communication.

Referring back to FIG. 2, subscriber lines 16 that do not share each ofthe same binder group segments 46 as each other may exhibit differentphysical and operational characteristics. Even subscribers 12 that arein near proximity to each other, such as in the same residentialneighborhood or in the same business development, may be coupled tocentral office 14 using subscriber lines 16 that do not share each ofthe same binder group segments 46.

Different subscriber lines 16 may extend from central office 14 andultimately reach the substantially same destination, such as the sameresidential neighborhood of subscribers 12, but may traverse differentdistances to reach their destinations. In this regard, the lengths ofsubscriber lines 16 in different binder group segments 46 may differalthough they service the same general population of subscribers 12. Thegauge of twisted pair wiring used for a particular subscriber line 16may also vary between binder group segments 46. Therefore, a subscriberline 16 may comprise a first gauge of twisted pair wiring, such astwenty-four gauge wiring, for the length of a first binder group segment46, and a second gauge of twisted pair wiring, such as twenty-six gaugewiring, for the length of a second binder group segment 46. Moreover,the number and type of noise and interference producing elements mayvary among binder group segments 46. Subscriber lines 16 sharing thesame binder group segment 46 may share the same noise information forthat length of segment 46. Subscriber lines 16 not sharing the samebinder group segments 46 may exhibit different noise characteristics. Asa result, the data rate capacity 80 or 82 of subscriber lines 16 maydiffer depending on their constituent binder group segments 46.

A particular advantage provided by system 10 is the ability to determinethe attenuation characteristics of individual binder group segments 46of subscriber lines 16. System management server 18 may then determinethe attenuation information of a selected subscriber line 16 accordingto the attenuation characteristics contributed by each of itsconstituent binder group segments 46. By determining attenuationinformation of a selected subscriber line 16 according to each of itsconstituent binder group segments 46, server 18 may more accuratelydetermine the data rate capacity 80 or 82 of a selected subscriber line16.

Referring in particular to the arrangement of subscriber lines 16illustrated in FIG. 2, each of subscribers 12 a-12 e, collectivelyreferred to as subscribers 12, are coupled to central office 14 usingsubscriber lines 16 a-16 e, collectively referred to as subscriber lines16, respectively. Subscriber lines 16 aand 16 b share a common bindergroup segment 46 ab. Subscriber lines 16 b, 16 d, and 16 e share acommon binder group segment 46 bde. Subscriber lines 16 c, 16 d, and 16e share a common binder group segment 46 cde.

The attenuation information for each subscriber line 16 at eachparticular sub-frequency of transmission comprises a combination of theattenuation information for its constituent binder group segments 46. Inparticular, the attenuation information, |H_(f)|, of a selectedsubscriber line 16 at a particular sub-frequency, f, is determined bymultiplying together in the frequency domain the attenuationinformation, |H_(f)|, for each of the constituent binder group segments46 of the selected subscriber line 16. For example, the attenuationinformation, |H_(f)|, for subscriber line 16 b comprises the attenuationinformation, |H_(f)|, for that segment of line 16 b in binder group 46ab multiplied in the frequency domain by the attenuation information,|H_(f)|, for that segment of line 16 b in binder group 46 bde.Similarly, the attenuation information for subscriber lines 16 d and 16e may be determined using the attenuation information, |H_(f)|, forthose segments of lines 16 d and 16 e in binder groups 46 de and 46 bde,as described above.

The attenuation information of subscriber lines 16 in binder groupsegment 46 ab may be different from that of the subscriber lines 16 inbinder group segment 46 cde due to the different length or gauge oftwisted pair wiring used in binder groups 46 ab and 46 cde. Therefore,although the attenuation information of subscriber lines 16 b and 16 dmay be similar for those segments of subscriber lines 16 b and 16 d incommon binder group 46 bde, the overall attenuation information forsubscriber lines 16 b and 16 d may differ due to differences in thephysical and operational characteristics of subscriber lines 16 inbinder group segments 46 ab and 46 cde.

Conversely, the attenuation characteristics of subscriber lines 16 d and16 e may be substantially similar since both share the same binder groupsegments 46 cde and 46 bde. Subscriber lines 16 d and 16 e thereforecomprise representative subscriber lines 16 for each other.

The following description of FIG. 2 details the determination of datarate capacity 80 and 82 of subscriber line 16 d for new subscriber 12 dusing, in a first method, the attenuation information of arepresentative subscriber line 16 e and, in a second method, theattenuation information for representative binder group segments 46 cdeand 46 bde.

According to the first method, if subscriber line 16 e receives dataservices from central office 14, then server 18 determines theattenuation and noise information of subscriber line 16 e based uponinformation collected by modems 60 during training, as described above.Database 22 stores this subscriber line information 28 for subscriberline 16 e. To determine the data rate capacity 80 or 82 of subscriberline 16 d, system management server 18 accesses subscriber lineinformation 28 in database 22 and determines that subscriber lines 16 dand 16 e share binder group segments 46 cde and 46 bde. Since subscriberlines 16 that share the same binder group segments 46 generally exhibitthe same physical and operational characteristics, the attenuation andnoise information stored for subscriber line 16 e is representative ofsubscriber line 16 d. In this regard, system management server 18 maydetermine the data rate capacity 80 or 82 of subscriber line 16 d usingthe attenuation and noise information stored in database 22 forrepresentative subscriber line 16 e. This method of determining datarate capacity 80 or 82 of subscriber line 16 d is particularlyadvantageous when a statistically significant number of representativesubscriber lines 16 exist.

In those instances where a representative subscriber line 16 does notexist for subscriber line 16 d, such as in a new residentialneighborhood or business development center where subscribers 12 havenot yet requested data services from central office 14, systemmanagement server 18 determines data rate capacity 80 or 82 using noiseinformation collected by a modem 42 operating as a spectrum analyzer onsubscriber line 16 d or calculated according to equations for FEXT andNEXT, as described above, and the attenuation information of itsconstituent binder group segments 46, as described in detail below. Todetermine the attenuation information of subscriber line 16 d, systemmanagement server 18 initially determines that subscriber line 16 dcomprises binder group segments 46 cde and 46 bde. The attenuationcontribution of subscriber lines 16 in binder group segment 46 cde maybe combined with that of subscriber lines 16 in binder group segment 46bde to determine the overall attenuation information for subscriber line16 d. In this regard, the breadth of subscriber line information 28stored in database 22 expands as the population of subscribers 12receiving data service from central office 14 grows.

The attenuation information for subscriber lines 16 in binder group 46cde may be determined based upon information collected by modems 60while providing data service to subscriber 12 c using subscriber line 16c. To determine the attenuation information of subscriber line 16 d,which comprises constituent binder group segments 46 cde and 46 bde,system management server 18 further determines the attenuationinformation for that segment of a subscriber line 16 in binder group 46bde. To do this, server 18 uses attenuation information stored indatabase 22 for subscriber lines 16 b and 16 a. In particular, server 18determines the attenuation information for that segment of a subscriberline 16 in binder group 46 bde according to the following equationscalculated in the frequency domain:${H_{f}}_{{binder}\quad {group}\quad {segment}\quad 46{bde}} = \frac{{H_{f}}_{{subscriber}\quad {line}\quad 16b}}{{H_{f}}_{{subscriber}\quad {line}\quad 16a}}$

where: |H_(f)|_(subscriber line 16b)=attenuation information forsubscriber line 16 b at sub-frequency (f); and

|H_(f)|_(subscriber line 16a)=attenuation information for subscriberline 16 a in binder group segment 46 ab at sub-frequency (f).

Therefore, if subscribers 12 a, 12 b, and 12 c receive data service fromcentral office 14, modems 60 may collect information during trainingthat defines the operational characteristics of subscriber lines 16 inbinder group segments 46 ab, 46 bde, and 46 cde. Based on thisinformation, server 18 may determine and database 22 may storeattenuation information for binder groups 46 cde and 46 bde. Systemmanagement server 18 combines the attenuation information for subscriberlines 16 in binder groups 46 cde and 46 bde according to the followingequation to determine the overall attenuation information of subscriberline 16 d:

|H_(f)|_(subscriber line 16d)=|H_(f)|_(binder group segment 46cde)×|H_(f)|_(binder group segment 46bde)

where: |H_(f)|_(binder group segment 46cde)=attenuation information forbinder group segment 46 cde of sub-frequency (f); and

|H_(f)|_(binder group segment 46bde)=attenuation information for bindergroup segment 46 bde at sub-frequency (f).

Server 18 determines the data rate capacity 80 or 82 of subscriber line16 d using the attenuation information of subscriber line 16 ddetermined above. This method for determining the data rate capacity ofa subscriber line 16 is particularly advantageous when attenuationinformation is stored in database 22 for a representative sample ofbinder group segments 46.

Although the description of FIG. 2 is detailed with reference todetermining the attenuation information of subscriber lines 16 in bindergroup segments 46 based upon information collected by modems 60 duringtraining, it should be understood that this information may also becollected using other methods. A central office 14 may obtain fieldmeasurements for attenuation in particular segments of binder groups 46at pertinent demarcation points in system 10. For example, centraloffice 14 may measure the attenuation characteristics of a subscriberline 16 in either binder group segment 46 ab or 46 cde at demarcationpoint 200 using the appropriate field measurement equipment. In thisregard, central office 14 may gather subscriber line information 28 forsubscriber lines 16 that may not currently support the provisioning ofdata services. A particular advantage provided by this aspect of system10 is that system management server 18 may expand the breadth ofsubscriber line information 28 stored in database 22 even if thepopulation of subscribers 12 receiving data service is small in aparticular region of system 10.

FIG. 3 illustrates the structure and content of subscriber lineinformation 28 stored in database 22. The multi-dimensional structure ofsubscriber line information 28 is represented in FIG. 3 as a cascadedset of two dimensional grids. Subscriber line information 28 may bearranged in subscriber line grid 300, binder groups grid 310, bindergroup disturbers grid 330, binder group attenuation grid 340, lineattenuation grid 360, and line noise grid 370. By maintaining,modifying, and updating the interrelationships and contents of thesegrids, system management server 18 establishes a relationship betweensubscriber lines 16, their binder group segments 46, and the attenuationand noise information of subscriber lines 16. Attenuation and noiseinformation for subscriber lines 16 helps determine the data ratecapacity 80 or 82 of a selected subscriber line 16, and the optimaltransmit power spectrum density of a modem 60 or 42 operating onsubscriber line 16.

Subscriber line grid 300 includes a row 302 for each subscriber line 16in system 10 and a column 304 for each binder group segment 46 of thatsubscriber line 16. Grid 300 further includes a column 306 to index arow of entries in each of line attenuation grid 360 and line noise grid370. In general, the information indexed by an entry in column 306 maybe used when subscriber line information 28 for the selected subscriberline 16 or a representative subscriber line 16 exists in database 22.

Binder groups grid 310 includes a row 312 for each binder group segment46 identified in subscriber line grid 300, and a column 314 for thelength of that binder group segment 46, a column 316 for the gauge oftwisted pair wiring used for that binder group segment 46, a column 318to index a row of entries in the binder group disturbers grid 330, and acolumn 320 to index a row of entries in the binder group attenuationgrid 340. The combination of subscriber line grid 300 and binder groupsgrid 310 provides an association between subscriber lines 16, theirbinder group segments 46, and the subscriber line information 28defining the physical and operational characteristics of thosesubscriber lines 16.

Binder group disturbers grid 330 includes a row 332 for each entry incolumn 318 of binder groups grid 310, and a column 334 indicating thenumber of each type of disturber found in a particular binder groupsegment 46. Different types of disturbers include bridged taps, otherxDSL services provided by subscriber lines 16 in a common binder groupsegment 46, radio frequency sources, or any other disturber in system10. Grid 330 may be updated to reflect the modification of subscriberlines 16 to add or remove those disturbers in communications system 10.

Binder group attenuation grid 340 includes a row 342 for each entry incolumn 320 of binder groups grid 310, and a column 344 for eachsub-frequency at which the attenuation information is determined for aparticular binder group segment 46 of a subscriber line 16. Thecombination of grids 310 and 340 establishes the attenuation informationof subscriber lines 16 in binder group segments 46 as a function offrequency. In this regard, grids 310 and 340 support determining thedata rate capacity 80 or 82 of a selected subscriber line 16 usingattenuation information for its constituent binder group segments 46.

Line attenuation grid 360 includes a row 362 for each entry of column306 of subscriber line grid 300, and a column 364 for each sub-frequencyat which the attenuation information is determined for a particularsubscriber line 16. Line noise grid 370 includes a row 372 for eachentry of column 306 of subscriber line grid 300, and a column 374 foreach sub-frequency at which the noise is determined for a particularsubscriber line 16. Generally, the combination of grids 360 and 370establish the attenuation information and noise information ofsubscriber lines 16 as a function of frequency. In this regard, grids360 and 370 support determining the data rate capacity 80 or 82 of aselected subscriber line 16 when subscriber line information 28 for theselected subscriber line 16 or a representative subscriber line 16exists in database 22.

Now referring to an exemplary arrangement of subscriber line information28 shown in FIG. 3, a subscriber line 16 represented by row 302 may beidentified using a phone number, an address, or some other uniqueidentifier for a subscriber 12 of a particular central office 14. Eachsubscriber line 16 may comprise a number of binder group segments 46represented by columns 304. Each binder group segment 46 in columns 304relates to a particular subscriber line 16 and identifies a portion ofthe physical and operational characteristics of the subscriber line 16in binder groups grid 310. Each subscriber line 16 also includes a“total line” column 306. Each entry 380 in column 306 relates to aparticular subscriber line 16 and identifies attenuation information andnoise information for the subscriber line 16 in line attenuation grid360 and line noise grid 370, respectively.

To determine the data rate capacity 80 or 82 of a selected subscriberline 16, server 18 determines its constituent binder group segments 46by referring to subscriber line grid 300. Upon determining theconstituent binder group segments 46 of the selected subscriber line 16,server 18 determines the data rate capacity 80 or 82 of subscriber line16 using attenuation information and noise information from grids 310,330, 340, 360, and 370. For example, server 18 searches for the selectedsubscriber line 16 or a representative subscriber line 16 in grid 300. Arepresentative subscriber line 16, as described above, is a subscriberline 16 having the same constituent binder group segments 46 as theselected subscriber line 16. Upon locating subscriber line information28 for the selected subscriber line 16 or for one or more representativesubscriber lines 16 in subscriber line grid 300, server 18 uses theappropriate pointers 382 and 384 indicated by entries 380 in column 306to access the appropriate rows 362 and 372 of line attenuation grid 360and line noise grid 370, respectively.

Line attenuation grid 360 provides attenuation information for theselected subscriber line 16 or a representative subscriber line 16 ateach sub-frequency of bandwidth available for transmission. Similarly,line noise grid 370 provides noise information for the selectedsubscriber line 16 or a representative subscriber line 16 at eachsub-frequency of bandwidth available for transmission. Server 18 may usethe attenuation information and noise information provided by grids 360and 370 to determine the data rate capacity 80 or 82 of the selectedsubscriber line 16, as discussed above with regard to FIG. 1.

System 10 may also determine attenuation information for a selectedsubscriber line 16 using the attenuation information of the constituentbinder group segments 46. For example, server 18 searches grid 300 foreach of the constituent binder group segments 46 which make up theselected subscriber line 16. For each constituent binder group segment46, server 18 uses the appropriate pointer 386 indicated by binder groupsegment 46 to identify the appropriate row 312 in binder groups grid310. Entry 390 of grid 310 indicates rows 342 of binder groupattenuation grid 340 using pointer 396. Binder group attenuation grid340 provides attenuation information for the representative binder groupsegments 46 at each sub-frequency of bandwidth available fortransmission.

Server 18 combines the attenuation information provided by grid 340 ateach identified sub-frequency of transmission for each of theconstituent binder group segments.46, as described above, to determinethe overall attenuation information for the selected subscriber line 16.Server 18 may then use the overall attenuation information to determinethe data rate capacity 80 or 82 of the selected subscriber line 16, asdescribed above with reference to FIG. 1.

System 10 may also determine noise information for a selected subscriberline 16 using noise information for the subscriber line 16, such as thenumber and type of disturbers affecting the selected subscriber line 16.For example, server 18 searches grid 300 for each of the constituentbinder group segments 46 which make up the selected subscriber line 16.For each constituent binder group segment 46, server 18 uses theappropriate pointer 386 indicated by binder group segment 46 to identifythe appropriate row 312 in binder groups grid 310. Entry 388 of grid 310indicates rows 332 of binder group disturbers grid 330 using pointer394. Binder group disturbers grid 330 indicates the number and type ofdisturbers for each representative binder group segment 46 of theselected subscriber line 16. Server 18 may determine the total noisecontributions upon selected subscriber line 16 by NEXT and FEXT asmodeled by the equations described above. Server 18 may then use theoverall noise information to determine the data rate capacity 80 or 82of the selected subscriber line 16, as described above with reference toFIG. 1. Server 18 may also determine the optimal transmit power spectrumdensity of a modem 60 operating on subscriber line 16, as describedabove with reference to FIG. 2, using the noise information stored indatabase 22.

FIG. 4 illustrates the structure and content of communication deviceinformation 29 stored in database 22. Communication device information29 may be arranged in a communication device grid 400 having a column402 to index communication devices, such as modems 60 of communicationserver 58; a column 404 to index the subscriber line 16 upon which aparticular modem 60 attempts to operate; a column 406 to index thecommunication protocol with which the particular modem 60 attempts tooperate; and a column 408 to index the number of failed attempts theparticular modem 60 has experienced using the subscriber line 16 and thecommunication protocol identified by columns 404 and 406, respectively.

The communication devices and subscriber lines indexed by columns 402and 404, respectively, may be identified using any suitableidentification or addressing techniques, such as by using telephonenumbers. The communication protocol indexed by column 406 may compriseany suitable communication protocol supported by the associatedsubscriber line 16. Server 18 dynamically updates communication devicegrid 400 to maintain a current association between a modem 60 and thenumber of times that the modem 60 fails an attempt to communicate usinga particular subscriber line 16 and a particular communication protocol.Because a subscriber line 16 generally identifies a particularcommunication device, such as a modem 42 residing at a subscriberpremises 12, grid 400 also identifies the number of times a modem 60fails an attempt to communicate with a particular modem 42.

Server 18 may determine that a particular modem 60 cannot establish aconnection with a particular modem 42, identified by a subscriber line16, using a first communication protocol, such as any of the xDSLcommunication protocols. In these instances, server 18 initiates theoperation of modem 60 to communicate with a modem 42 using analternative communication protocol. For example, modems 60 and 42 mayoperate using any of the V-series communication protocols, such as theV.90 communication protocol, or using an Integrated Services DigitalNetwork (ISDN) communication protocol. In addition, server 18 mayinitiate the operation of modems 60 and 42 using a first alternativecommunication protocol for downlink data communication and a secondalternative communication protocol for uplink data communication. Forexample, server 18 may initiate the operation of modem 60 using the V.90communication protocol for downlink data communication and using theV.34 communication protocol for uplink data communication. In aparticular embodiment, server 18 initiates the operation of modems 60and 42 over any suitable range of sub-frequencies in the voice frequencyspectrum.

Server 18 may determine that the particular modem 60 cannot communicatewith a particular modem 42 using a particular communication protocol ina number of ways. For example, server 18 may monitor grid 400 todetermine the number of times a particular modem 60 fails an attempt tocommunicate with a particular modem 42 using a particular communicationprotocol. If the number of times the modem 60 fails an attempt tocommunicate with the particular modem 42 exceeds a predeterminedthreshold, then server 18 initiates the operation of the modem 60 usingan alternative communication protocol supported by the particularsubscriber line 16. Referring to FIG. 4, for example, if the threefailed connection attempts by the modem 60 identified by the telephonenumber 214-555-2163 exceeds a predetermined threshold established byserver 18, then server 18 initiates the operation of that modem 60 forsubscriber line 16 identified by the telephone number 214-555-8818 usingan alternative communication protocol.

In another example, server 18 may determine that thesignal-to-noise-ratio of a subscriber line 16, as determined usingtechniques described with respect to FIG. 1, fails to exceed apredetermined threshold such that the subscriber line 16 cannot supporta particular communication protocol, such as an xDSL communicationprotocol. In this instance, server 18 may initiate the operation ofmodem 60 using an alternative communication protocol that may besupported by the particular subscriber line 16. As described above,either excessive noise or attenuation affecting a subscriber line 16 maycause a decrease in the signal-to-noise ratio of a subscriber line 16.If server 18 later determines that the signal-to-noise-ratio of thesubscriber line 16 is sufficient to support the previously attemptedcommunication protocol, due to a decrease in noise or attenuationaffecting the subscriber line 16, for example, then server 18 may againinitiate operation of a modem 60 operating on the particular subscriberline 16 using the previously attempted communication protocol.

In yet another example, server 18 may determine that the modem 42 withwhich a particular modem 60 is attempting to communicate cannot supportcommunication using a particular communication protocol, such as an xDSLcommunication protocol. In this instance, server 18 initiates theoperation of modem 60 using an alternative communication that issupported by modem 42, such as a V-series communication protocol.Although the determination of whether a modem 60 may establish aconnection with a modem 42 has been described with reference to threespecific examples, it should be understood that the present inventioncontemplates initiating the operation of a modem 60 using an alternativecommunication protocol in response to any determination by server 18that modem 60 is inoperable to communicate with modem 42 using a firstcommunication protocol.

By determining that a modem 60 is inoperable to communicate with a modem42 using a first communication protocol and, in response, initiating theoperation of modem 60 using an alternative communication protocol,system 10 provides significant technical advantages. First,communication server 58 establishes more reliable connectivity between amodem 60 and a modem 42. Therefore, a subscriber 12 is less likely tosuffer a loss of data services. Furthermore, communication server 58need not maintain a connection with a global-communication-networkservice provider having an analog communication device coupled to theplain old telephone service (POTS), such as an Internet provider (ISP),in order to provide data services to a subscriber 12. Instead of such anarrangement where additional switching components are required toterminate the subscriber line 16 using an analog communication device,system 10 terminates the subscriber line 16 using a digitalcommunication device. In particular, modems 60 communicate withcommunication network 70 using network device 68 of DSLAM 69. In thisrespect, the subscriber lines 16 of system 10 are terminated at each endusing digital communication devices and, therefore, system 10 mayprovide a more robust compliment of data services to subscribers 12.Other advantages include a potentially higher data rate capacity 80 and82 for subscriber lines 16 and an increased sampling frequency andassociated signal-to-noise ratio for subscriber line 16. Of course,system 10 may still terminate a connection with a modem 42 using ananalog communication device associated with POTS.

FIG. 5 illustrates a method for managing subscriber line information 28for communication system 10. The method begins at step 410 where systemmanagement server 18 extracts subscriber line information 28 fromvarious components of system 10 including, for example, information 28from a plurality of communication servers 58. Typically, this subscriberline information 28 comprises information defining the operationalcharacteristics of subscriber line 16 gathered by modem 60 during modemtraining. Alternatively, subscriber line information 28 comprisesinformation gathered by modems 60 and 42 operating in a diagnostic mode.In a particular embodiment, information 28 extracted by server 18comprises the transmit power spectrum density, Q_(f), and the receivedpower spectrum density, S_(f), of a data signal communicated between amodem 60 and a modem 42 for each channel of the data frequency spectrumsupported by a particular subscriber line 16.

Server 18 determines the attenuation information and noise informationfor subscriber lines 16 at steps 412 and 414, respectively, using thesubscriber line information 28 extracted at step 410 and the attenuationand noise modeling techniques described above with reference to FIG. 1.In a particular embodiment, server 18 determines the attenuationinformation for subscriber lines 16 according to their constituentbinder group segments 46, as described above with reference to FIG. 2.Server 18 determines noise information for subscriber lines 16 bymeasuring noise characteristics of a subscriber line 16 duringoperation, or by calculating the noise information using subscriber lineinformation 28 for subscriber line 16, as described above with referenceto FIG. 1. System management server 18 stores the attenuation and noiseinformation for subscriber lines 16 in database 22 at step 416. In oneembodiment, server 18 stores this information for each subscriber line16 according to its constituent binder group segments 46, as describedabove with reference to FIG. 3. Execution terminates at step 418.

FIG. 6 illustrates a method for determining the transmit power spectrumdensity of a modem 60 or 42 operating on a subscriber line 16. System 18identifies a subscriber line 16 at step 450. The identified subscriberline 16 may be used by system 10 to provide data services to a newsubscriber 12. The provisioning of data services to a new subscriber 12over a subscriber line 16 in a particular binder group segment 46 maycontribute to the noise and distortion upon other subscriber lines 16within the same binder group segment 46, thereby degrading the servicesalready provided to other subscribers 12 unless the noise contributed bythe identified subscriber line 16 is maintained below a determined“noise floor.” System 10 identifies subscriber lines 16 having a commonbinder group segment 46 with identified subscriber line 16, at step 452.System 10 determines noise information for subscriber lines 16 in thecommon binder group segment 46 at step 454, as described above withreference to FIG. 1. In one embodiment, the determined noise informationcomprises the noise information for the identified subscriber line 16.

System 10 determines cross-channel-coupling information for subscriberlines 16 at step 456. Database 22 stores the noise information and thecross-channel-coupling information as subscriber line information 28 atstep 458. System 10 determines the transmit power spectrum density ofmodems 60 or 42 operating on the identified subscriber line 16 at step460, based upon the determined noise and cross-channel-couplinginformation.

In one embodiment, system 10 determines the transmit power spectrumdensity of modems 60 or 42 proportional to the noise information for theidentified subscriber line 16 and inversely proportional to thecross-channel-coupling information. System 10 selects the appropriatecommunication protocol for modems 60 or 42 operating on identifiedsubscriber line 16 at step 462, based upon the determined transmit powerspectrum density, as described above with reference to FIG. 2. Themethod concludes at step 464.

FIG. 7 illustrates a method for determining the data rate capacity 80 or82 of a selected subscriber line 16 of communication system 10. System10 receives a request to determine the data rate capacity 80 or 82 of aselected subscriber line 16 at step 500. System 10 retrieves subscriberline information 28 from database 22 according to the selectedsubscriber line 16, a representative subscriber line 16, or theconstituent binder group segments 46 of the selected subscriber line 16,at steps 502.

Referring to steps 502, server 18 retrieves attenuation information forthe selected subscriber line 16 at step 510, using one of two methods.According to a first method, server 18 retrieves attenuation informationfor a representative subscriber line 16, as described with reference toFIG. 3. According to a second method, server 18 retrieves attenuationinformation for each of the constituent binder group segments 46 of theselected subscriber line 16 and associates each of their individualattenuation contributions to determine the approximate total attenuationinformation for the selected subscriber line 16. Server 18 retrievesnoise information for the selected subscriber line 16, at step 512,using one of two methods. According to a first method, server 18retrieves noise information that is determined using the noisecalculation techniques or noise measurement techniques described abovewith reference to FIG. 1. According to a second method, server 18retrieves noise information for a representative subscriber line 16.Server 18 determines the appropriate signal-to-noise ratios ofsubscriber-line 16 at step 520 using the attenuation information andnoise information determined at steps 510 and 512, respectively, asdescribed above with reference to FIG. 1. Server 18 determines the datarate capacity 80 or 82 of selected subscriber line 16 at step 502 usingthe signal-to-noise ratios determined at step 522. Execution terminatesat step 524.

FIG. 8 illustrates a method for determining a communication protocol ofa communication device 60 operating on a subscriber line 16 of system10. The method begins at step 600 where server 18 selects acommunication protocol with which to operate modem 60. Typically, server18 initially attempts to operate modem 60 using an xDSL communicationprotocol. Modem 60 attempts to connect with modem 42 using the selectedcommunication protocol at step 602. A counter is initialized to one atstep 604 to signify the number of attempts made by the particular modem60 to connect with a particular modem 42 using the selectedcommunication protocol. Server 18 updates communication deviceinformation 29 stored in database 22 at step 606.

Server 18 determines whether the attempt to establish a connectionbetween the particular modems 60 and 42 using the selected communicationprotocol failed at step 608. If so, execution proceeds to step 610 whereserver 18 increments the counter by one. Server 18 determines whetherthe counter is greater than a predetermined threshold at step 612. Inparticular, server 18 establishes a predetermined number of failedattempts to connect that a particular modem 60 may experience beforeattempting a connection using an alternative communication protocol. Ifthe counter does not exceed the predetermined threshold as determined atstep 612, then execution proceeds to step 614 where modem 60 retries anattempt to connect with the particular modem 42 using the currentlyselected communication protocol. Execution then proceeds to step 606. Ifthe counter exceeds the predetermined threshold as determined at 612,then execution proceeds to step 616 where server 18 selects analternative communication protocol with which to connect modems 60 and42. In one embodiment, server 18 selects a V-series communicationprotocol to connect modems 60 and 42. Execution then returns to step602.

If modem 60 does not fail to connect with modem 42 as determined at step608, execution proceeds to step 618 where server 18 initiates theoperation of modem 60 using the selected communication protocol.Communication server 58 provides data services to subscriber 12 at step620 using the connection established between modems 60 and 42.Communication server 58 terminates the connection between modems 60 and42 at step 622. Execution terminates at step 624.

What is claimed is:
 1. A communication system for determining the datarate capacity of a twisted pair subscriber line, comprising: acommunication server coupled to a plurality of subscribers using aplurality of subscriber lines, wherein a first subscriber line comprisesa first binder group segment and a second binder group segment, and asecond subscriber line comprises the first binder group segment and thesecond binder group segment; a memory coupled to the communicationserver and storing attenuation information for the first binder groupsegment and the second binder group segment associated with the secondsubscriber line; and a processor coupled to the memory and operable todetermine the data rate capacity of a first subscriber line using theattenuation information for the first binder group segment and thesecond binder group segment associated with the second subscriber line.2. The communication system of claim 1, wherein: each of the pluralityof subscriber lines comprises a plurality of binder group segments; andthe memory stores attenuation information for a particular subscriberline indexed by the binder group segments of the particular subscriberline.
 3. The communication system of claim 1, wherein: the memory storesnoise information for the second subscriber line; and the processor isfurther operable to determine the data rate capacity of the firstsubscriber line using the noise information associated with the secondsubscriber line.
 4. The communication system of claim 1, wherein: athird subscriber line comprises the second binder group segment; thememory stores attenuation information for the second binder groupsegment associated with the third subscriber line; and the processordetermines the data rate capacity of the first subscriber line using theattenuation information for the second binder group segment associatedwith the third subscriber line.
 5. The communication system of claim 1,wherein: the first subscriber line comprises a plurality of binder groupsegments; the memory stores attenuation information for at least one ofthe binder group segments of the first subscriber line; the secondsubscriber line comprises a plurality of binder group segments; and theprocessor determines the attenuation information of at least one of thebinder group segments of the second subscriber line using theattenuation information stored for at least one of the binder groupsegments of the first subscriber line.
 6. The communication system ofclaim 1, wherein: the communication server comprises a firstcommunication device operable to communicate a signal at a transmitpower using a particular subscriber line; a subscriber coupled to thecommunication server using the particular subscriber line comprises asecond communication device operable to receive the signal at a receivepower; and the processor is operable to determine the attenuationinformation for the particular subscriber line using the transmit powerand the receive power of the signal.
 7. The communication system ofclaim 6, wherein the memory stores the determined attenuationinformation indexed by the particular subscriber line.
 8. Thecommunication system of the claim 6, wherein: the particular subscriberline comprises a plurality of binder group segments; the processor isoperable to determine the attenuation information for each binder groupsegment of the particular subscriber line; and the memory stores theattenuation information for the particular subscriber line indexed bythe binder group segments.
 9. The communication system of claim 1,wherein: the first subscriber line is associated with a particularbinder group; the memory stores information for the number and type ofdisturbers associated with the particular binder group; and theprocessor is operable to determine the noise information for the firstsubscriber line using the information for the number and type ofdisturbers.
 10. The communication system of claim 1, wherein: thecommunication server comprises a first communication device operable tocommunicate a signal using a particular subscriber line; a subscribercoupled to the communication server using the particular subscriber linecomprises a second communication device operable to receive the signaland to determine noise information of the signal for communication tothe first communication device; and the processor is further operable todetermine noise information for the particular subscriber line basedupon the noise information of the signal.
 11. The communication systemof claim 10, wherein: the particular subscriber line supportscommunication using a particular frequency spectrum; and the processordetermines the noise information of the signal for the frequencyspectrum using noise information for the signal measured for asub-frequency of the frequency spectrum.
 12. The communication system ofclaim 1, wherein the first subscriber line supports uplink and downlinkdata communication and the data rate capacity comprises a first datarate capacity associated with the uplink data communication and a seconddata rate capacity associated with the downlink data communication. 13.The communication system of claim 1, wherein: the communication servercomprises a first communication server; the communication system furthercomprises a second communication server coupled to the subscribers; andthe memory is further operable to store first subscriber lineinformation received from the first communication server and secondsubscriber line information received from the second communicationserver.
 14. A method for determining the data rate capacity of a twistedpair subscriber line, comprising: storing attenuation information andnoise information for a plurality of twisted pair subscriber lines thatcouple a plurality of subscribers to a communication server, wherein afirst subscriber line comprises a first binder group segment and asecond binder group segment, and a second subscriber line comprises thefirst binder group segment and the second binder group segment; anddetermining the data rate capacity of the first subscriber line usingnoise information stored for the first binder group segment and thesecond binder group segment associated with the second subscriber line.15. The method of claim 14, wherein each of the plurality of subscriberlines comprises a plurality of binder group segments, and furthercomprising the attenuation information and the noise information for aparticular subscriber line by the binder group segments of theparticular subscriber line.
 16. The method of claim 14, wherein: storingcomprises storing attenuation information for the first binder groupsegment and the second binder group segment associated with the secondsubscriber line; and determining comprises determining the data ratecapacity of the first subscriber line using the attenuation informationfor the first binder group segment and the second binder group segmentassociated with the second subscriber line.
 17. The method of claim 14,wherein: a third subscriber line comprises the second binder groupsegment; storing comprises storing attenuation information for thesecond binder group segment associated with the third subscriber line;and determining comprises determining the data rate capacity of thefirst subscriber line using the attenuation information for the secondbinder group segment associated with the third subscriber line.
 18. Themethod of claim 14, wherein the first subscriber line comprises aplurality of binder group segments and the second subscriber linecomprises a plurality of binder group segments, the method furthercomprising: storing attenuation information for at least one of thebinder group segments of the first subscriber line; and determining theattenuation information of at least one of the binder group segments ofthe second subscriber line using the attenuation information stored forat least one of the binder group segments of the first subscriber line.19. The method of claim 14, further comprising: communicating a signalat a transmit power using a particular subscriber line; receiving thesignal at a receive power; and determining the attenuation informationfor the particular subscriber line using the transmit power and thereceive power of the signal.
 20. The method of claim 19, wherein storingcomprises storing the determined attenuation information indexed by theparticular subscriber line.
 21. The method of claim 19, wherein theparticular subscriber line comprises a plurality of binder groupsegments, the method further comprising: determining the attenuationinformation for each binder group segment of the particular subscriberline; and storing the attenuation information for the particularsubscriber line indexed by the binder group segments.
 22. The method ofclaim 14, wherein the first subscriber line is associated with aparticular binder group, the method further comprising: storinginformation for the number and type of disturbers associated with theparticular binder group; and determining the noise information for thefirst subscriber line using the information for the number and type ofdisturbers.
 23. The method of claim 14, further comprising:communicating a signal using a particular subscriber line; determiningnoise information for the signal; determining noise information for theparticular subscriber line based upon the noise information for thesignal; and storing in a memory the noise information for the particularsubscriber line.
 24. The method of claim 23, wherein the particularsubscriber line supports communication using a particular frequencyspectrum, the method further comprising: measuring the noise informationof the signal for a sub-frequency of the frequency spectrum; anddetermining the noise information of the signal for the frequencyspectrum based upon the noise information of the signal for thesub-frequency of the frequency spectrum.
 25. The method of claim 14,wherein the first subscriber line supports uplink and downlink datacommunication and the data rate capacity comprises a first data ratecapacity associated with the uplink data communication and a second datarate capacity associated with the downlink data communication.
 26. Themethod of claim 14, further comprising: receiving first subscriber lineinformation from a first communication server; receiving secondsubscriber line information from a second communication server; storingthe first subscriber line information; and storing the second subscriberline information.
 27. A communication facility for determining the datarate capacity of a twisted pair subscriber line, comprising: a memorythat stores attenuation information and noise information for aplurality of subscriber lines that couple a plurality of subscribers toa communication server; and a processor coupled to the memory andoperable to determine the data rate capacity of a first subscriber lineusing at least one of the attenuation information and the noiseinformation stored for a second subscriber line; wherein: the firstsubscriber line comprises a plurality of binder group segments; thememory stores attenuation information for at least one of the bindergroup segments of the first subscriber line; the second subscriber linecomprises a plurality of binder group segments; and the processordetermines the attenuation information of at least one of the bindergroup segments of the second subscriber line using the attenuationinformation stored for the binder group segments of the first subscriberline.
 28. The communication facility of claim 27, wherein: each of theplurality of subscriber lines comprises a plurality of binder groupsegments; and the memory stores attenuation information for a particularsubscriber line indexed by the binder group segments of the particularsubscriber line.
 29. The communication facility of claim 27, wherein:the first subscriber line comprises a first binder group segment and asecond binder group segment; the second subscriber line comprises thefirst binder group segment and the second binder group segment; thememory stores attenuation information for the first binder group segmentand the second binder group segment associated with the secondsubscriber line; and the processor determines the data rate capacity ofthe first subscriber line using the attenuation information for thefirst binder group segment and the second binder group segmentassociated with the second subscriber line.
 30. The communicationfacility of claim 27, wherein: the first subscriber line comprises afirst binder group segment and a second binder group segment; the memorystores noise information for the second subscriber line comprising thefirst binder group segment and the second binder group segment; and theprocessor determines the data rate capacity of the first subscriber lineusing the noise information associated with the second subscriber line.31. The communication facility of claim 27, wherein: the firstsubscriber line comprises a first binder group segment and a secondbinder group segment; the second subscriber line comprises the firstbinder group segment; a third subscriber line comprises the secondbinder group segment; the memory stores attenuation information for thefirst binder group segment associated with the second subscriber line,and for the second binder group segment associated with the thirdsubscriber line; and the processor determines the data rate capacity ofthe first subscriber line using the attenuation information for thefirst binder group segment associated with the second subscriber lineand the second binder group segment associated with the third subscriberline.
 32. The communication facility of claim 27, wherein the processoris further operable to determine the attenuation information for aparticular subscriber line using subscriber line information receivedfrom the communication server.
 33. The communication facility of claim32, wherein the memory stores the determined attenuation informationindexed by the particular subscriber line.
 34. The communicationfacility of claim 32, wherein: the particular subscriber line comprisesa plurality of binder group segments; the processor is operable todetermine the attenuation information for each binder group segment ofthe particular subscriber line; and the memory stores the attenuationinformation for the particular subscriber line indexed by the bindergroup segments.
 35. The communication facility claim 27, wherein: thefirst subscriber line is associated with a particular binder group; thememory stores information for the number and type of disturbersassociated with the particular binder group; and the processor isoperable to determine the noise information for the first subscriberline using the information for the number and type of disturbers. 36.The communication facility of claim 27, wherein the first subscriberline supports uplink and downlink data communication and the data ratecapacity comprises a first data rate capacity associated with the uplinkdata communication and a second data rate capacity associated with thedownlink data communication.
 37. The communication facility of claim 27,wherein the memory is further operable to store first subscriber lineinformation received from a first communication server and secondsubscriber line information received from a second communication server.38. A communication facility for determining the data rate capacity of atwisted pair subscriber line, comprising: means for storing attenuationinformation and noise information for a plurality of subscriber linesthat couple a plurality of subscribers to a communication servers,wherein a first subscriber line comprises a first binder group segmentand a second binder group segment, and a second subscriber linecomprises the first binder group segment and the second binder groupsegment; and means for determining the data rate capacity of a firstsubscriber line using at least one of the attenuation information andthe noise information stored for the first binder group segment and thesecond binder group segment of the second subscriber line.
 39. Acommunication facility for determining the data rate capacity of atwisted pair subscriber line, comprising: a memory that storesattenuation information and noise information for a plurality ofsubscriber lines that couple a plurality of subscribers to acommunication server, wherein the first subscriber line comprises afirst binder group segment and a second binder group segment and thesecond subscriber line comprises the first binder group segment and thesecond binder group segment; and a processor coupled to the memory andoperable to determine the data rate capacity of a first subscriber lineusing at least one of the attenuation information and the noiseinformation stored for the first binder group segment and the secondbinder group segment associated with the second subscriber line.